The phrase theme music usually refers to that of a radio program, television program, or movie. It is a piece that is often written specifically for that show, and usually played during the title sequence and/or end credits. If it is accompanied by lyrics, most often associated with the show, it is a theme song.
The phrase theme song or signature tune may also be used to refer to a song that has become especially associated with a particular performer or dignitary; often used as they make an entrance. Examples of this association include: the President of the United States with "Hail to the Chief"; Bob Hope with "Thanks for the Memory"; Frank Sinatra with "New York, New York" and "My Way"; Liberace with "I'll Be Seeing You."
The purpose of a theme song is often similar to that of a leitmotif.
